Thermoplastic bristles that are both solid and hollow have been employed in applicator brushes, such as paintbrushes. Moreover, hollow bristles having a single central passage with radiating spokes, as well as honeycomb bristles having two semi-cylindrical passages without radiating spokes have been employed in applicator brushes. All of these prior art structures have one or more deficiencies that are overcome by the present invention.
Solid bristles, although being sufficiently durable for use in commercial brushes, do have certain drawbacks relative to hollow bristles for applicator brushes. In particular, solid bristles are harder to flag than hollow bristles, and, do to their higher bulk density than void-containing bristles (e.g., hollow bristles and honeycomb bristles) such solid bristles provide lower yields in the manufacture of applicator brushes, i.e., the bristle weight per brush is higher when solid bristles are used than when void-containing bristles are employed. Although hollow bristles having a single central passage, both with and without radiating spokes, and honeycomb bristles having a pair of internal semi-cylindrical passages separated by a dividing wall can be made with less polymer than solid bristles, and therefore provide higher yields in the manufacture of applicator brushes than employing solid bristles, they have other deficiencies. In particular, hollow bristles having a single central passage are often weaker than desired, and also tend to receive paint (or other viscous liquid to be applied) deep into the interior of the passage, thereby making it difficult to effectively clean brushes employing such bristles. Moreover, such hollow bristles have limited polymer surface area for flagging to enhance the evenness of application of paint or other viscous fluids. Although adding radiating spokes to the hollow bristles does increase the surface area of polymer that can be flagged, such bristles still tend to be weaker than desired, and still are susceptible of receiving paint or other viscous liquids excessively deep into the interior of the cylindrical opening.
Honeycomb bristles, by virtue of having a central polymer wall dividing the two semi-cylindrical passages, do tend to have increased strength relative to hollow bristles. In addition the central wall constitutes an additional polymer surface that can be flagged to enhance the evenness of distribution of high viscosity fluids, such as paint. Moreover, by including a central wall dividing the central passage into two semi-cylindrical passages, each of such passages is less than one-half the area of a single cylindrical passage in a hollow bristle of the same diameter as the honeycomb bristle. These more restricted passages are less likely to receive high viscosity fluids, such as paint, undesirably deep into the interior thereof to impair the cleaning efficiency of brushes employing such bristles.
In spite of the positive attributes of a variety of the bristles identified above, a need still exists for new bristle constructions having relatively high yields in the manufacture of applicator brushes, and that have improved performance characteristics, thereby making them well-suited for use primarily for consumer (as opposed to professional) brush applications. It is to such bristles and applicator brushes employing such bristles that the present invention relates.